2.2.0.7 true Significant Accounting Policies (Details) (USD $) 4010 - Disclosure - Significant Accounting Policies (Details) true false In Millions false false 1 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ 2 Significant Accounting Policies 2 ceg_SignificantAccountingPoliciesDisclosureAbstract ceg false na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 3 Number of consolidated variable interest entities 2 ceg_NumberOfVariableInterestEntities ceg false na instant The number of variable interest entities consolidated in the reporting entity's consolidated financial statements. false false false false false false false false false false false terselabel false 1 false true false false 3 3 false false false 2 false false false false 0 0 false false false xbrli:integerItemType integer The number of variable interest entities consolidated in the reporting entity's consolidated financial statements. No authoritative reference available. false 4 Low end of the range of the required percentage voting interest held to account for investments with the equity method of accounting (in hundredths) 2 ceg_PercentageOfInterestHeldForEquityMethodInvestmentsLowEndOfRange ceg false na duration The low end of the range of the required percentage voting interest to be held by the reporting entity to use the equity... false false false false false false false false false false false verboselabel false 1 false true false false 0.20 0.20 false false false 2 false false false false 0 0   false false false us-types:percentItemType pure The low end of the range of the required percentage voting interest to be held by the reporting entity to use the equity method of accounting to report investments, corporate joint ventures, partnerships and affiliated companies in its consolidated financial statements. If the reporting entity can exercise control over the operations and policies, accounting rules require consolidation of the investee's financial statements. No authoritative reference available. false 5 High end of the range of the required percentage voting interest held to account for investments with the equity method of accounting (in hundredths) 2 ceg_PercentageOfInterestHeldForEquityMethodInvestmentsHighEndOfRange ceg false na duration The high end of the range of the required percentage voting interest to be held by the reporting entity to use the equity... false false false false false false false false false false false verboselabel false 1 false true false false 0.5001 0.5001 false false false 2 false false false false 0 0   false false false us-types:percentItemType pure The high end of the range of the required percentage voting interest to be held by the reporting entity to use the equity method of accounting to report investments, corporate joint ventures, partnerships and affiliated companies in its consolidated financial statements. If the reporting entity can exercise control over the operations and policies, accounting rules require consolidation of the investee's financial statements. No authoritative reference available. false 6 Threshold percentage of voting interest held for investments recorded with the cost method of accounting (in hundredths) 2 ceg_PercentageOfInterestHeldForCostMethodInvestmentsThreshold ceg false na duration The threshold for percentage voting interest held used by the reporting entity to account for its investments using the cost... false false false false false false false false false false false terselabel false 1 false true false false 0.20 0.20 false false false 2 false false false false 0 0   false false false us-types:percentItemType pure The threshold for percentage voting interest held used by the reporting entity to account for its investments using the cost method of accounting. No authoritative reference available. false 7 Percent of membership interest in CENG sold (in hundredths) 2 ceg_MembershipInterestSalePercentage ceg false na instant The percentage of ownership interest in a subsidiary that was sold during the period. false false false false false false false false false false false terselabel false 1 false true false false 0.4999 0.4999 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure The percentage of ownership interest in a subsidiary that was sold during the period. No authoritative reference available. false 8 Term of suspension of collecting shareholder return component of the administrative fee for residential SOS service by BGE (in years) 2 ceg_TermOfSuspensionOfShareholderReturnComponentBySubsidiaryYears ceg false na duration This element represents the term, in years, of the suspension of collecting the shareholder return component of the... false false false false false false false false false false false terselabel false 1 false true false false 10 10 false false false 2 false false false false 0 0 false false false xbrli:integerItemType integer This element represents the term, in years, of the suspension of collecting the shareholder return component of the administrative fee for standard offer services to residential customers by a subsidiary. No authoritative reference available. false 9 Rate cap for BGE residential electric customers from July 1, 2006 until May 31, 2007 (in hundredths) 2 ceg_RateCapImposedOnPublicUtilitySubsidiary ceg false na instant This element represents the rate cap imposed on a public utility subsidiary of the reporting entity. false false false false false false false false false false false terselabel false 1 false true false false 0.15 0.15 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure This element represents the rate cap imposed on a public utility subsidiary of the reporting entity. No authoritative reference available. false 10 Rate increase cap ordered by the Maryland PSC for BGE's electric distribution case to be filed at any time beginning in January 2010 (in hundredths) 2 ceg_RateIncreaseCapForMaximumIncreaseInFirstElectricDistributionRateCase ceg false na instant This element represents the rate increase cap imposed on a public utility subsidiary by the public service commission. false false false false false false false false false false false terselabel false 1 false true false false 0.05 0.05 false false false 2 false false false false 0 0   false false false us-types:percentItemType pure This element represents the rate increase cap imposed on a public utility subsidiary by the public service commission. No authoritative reference available. false 11 Minimum percentage of fixed-price contracts for forecasted system supply requirements for the November through March period required by the public service commission to be procured by BGE (in hundredths) 2 ceg_MinimumPercentageOfForecastedSystemSupplyRequirementsRequiredToBeProcuredBySubsidiary ceg false na instant This element represents the minimum percentage of fixed-price contracts for forecasted system supply requirements required of... false false false false false false false false false false false terselabel false 1 false true false false 0.10 0.10 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure This element represents the minimum percentage of fixed-price contracts for forecasted system supply requirements required of a public utility subsidiary by the public service commission. No authoritative reference available. false 12 Maximum percentage of fixed-price contracts for forecasted system supply requirements for the November through March period required by the public service commission to be procured by BGE (in hundredths) 2 ceg_MaximumPercentageOfForecastedSystemSupplyRequirementsRequiredToBeProcuredBySubsidiary ceg false na instant This element represents the maximum percentage of fixed-price contracts for forecasted system supply requirements required of... false false false false false false false false false false false terselabel false 1 false true false false 0.20 0.20 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure This element represents the maximum percentage of fixed-price contracts for forecasted system supply requirements required of a public utility subsidiary by the public service commission. No authoritative reference available. false 13 Cash collateral held from counterparties related to wholesale marketing and risk management activities 2 ceg_CashCollateralHeldFromCounterparties ceg false debit instant The carrying amount (fair value) as of the balance sheet date of cash held as collateral from counterparties. false false false false false false false false false false false terselabel false 1 true true false false 95200000 95.2 false false false 2 true true false false 258300000 258.3 false false false xbrli:monetaryItemType monetary The carrying amount (fair value) as of the balance sheet date of cash held as collateral from counterparties. No authoritative reference available. false 14 Fair value of power purchase agreement with CENG 2 ceg_FairValueRelatedPartyAgreementAtClosing ceg false debit instant Fair value of power purchase agreement with CENG recorded at closing. false false false false false false false false false false false terselabel false 1 true true false false 800000000 800.0 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary Fair value of power purchase agreement with CENG recorded at closing. No authoritative reference available. false 15 Concentration of credit risk trigger for disclosure, percentage (in hundredths) 2 ceg_ConcentrationOfCreditRiskExposurePercentage ceg false na instant The percentage credit exposure of the entity to any single obligor or counterparty (including a collection of counterparties... false false false false false false false false false false false terselabel false 1 false true false false 0.10 0.10 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure The percentage credit exposure of the entity to any single obligor or counterparty (including a collection of counterparties based in a single country other than the United States) that is considered to be a significant concentration of credit risk. No authoritative reference available. false 16 Counterparties exceeding the maximum credit exposure trigger percentage, number 2 ceg_ConcentrationOfCreditRiskCounterpartiesExceedingMaximumCreditExposureTriggerPercentageNumber ceg false na instant The number of counterparties exceeding the maximum credit exposure trigger percentage. false false false false false false false false false false false terselabel false 1 false true false false 1 1 false false false 2 false false false false 0 0 false false false xbrli:integerItemType integer The number of counterparties exceeding the maximum credit exposure trigger percentage. No authoritative reference available. false 17 Percent of credit risk exposure in CENG (in hundredths) 2 ceg_PercentageOfConcentrationOfCreditRiskAttributableToRelatedParty ceg false na instant This element represents the reporting entity's percentage of credit risk exposure with a related party. false false false false false false false false false false false terselabel false 1 false true false false 0.25 0.25 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure This element represents the reporting entity's percentage of credit risk exposure with a related party. No authoritative reference available. false 18 Baltimore Gas and Electric Company 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosuresignificantaccountingpoliciesdetails false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 3 USD true false false false Baltimore Gas and Electric Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ false 4 USD true false false false Baltimore Gas and Electric Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ na No definition available. No authoritative reference available. false 19 Significant Accounting Policies 2 ceg_SignificantAccountingPoliciesDisclosureAbstract ceg false na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 27 Rate increase cap ordered by the Maryland PSC for BGE's electric distribution case to be filed at any time beginning in January 2010 (in hundredths) 2 ceg_RateIncreaseCapForMaximumIncreaseInFirstElectricDistributionRateCase ceg false na instant This element represents the rate increase cap imposed on a public utility subsidiary by the public service commission. false false false false false false false false false false false terselabel false 1 false true false false 0.05 0.05 false false false 2 false false false false 0 0   false false false us-types:percentItemType pure This element represents the rate increase cap imposed on a public utility subsidiary by the public service commission. No authoritative reference available. false 2 19 false HundredThousands UnKnown UnKnown false true